Method of producing articles from sheet material



y A.- KRQNQUEST 2,086,166

METHOD OF PRODUCING ARTICLES FROM SHEET MATERIAL Filed Jul 24, 195

Patented July 6, 1937 METHOD OF PRODUCING ARTICLES snnn'r MATERIAL FROMl-Alfred L. Kronquest, Syracuse. N. asslgnor to Continental Can Company,Inc., New

N. Y., a corporation Application f July 24,

2 Claims.

The invention relates to new and usefuI im provements in a. method ofproducing articles from metal coated sheet steel and the productproduced thereby.

An object of the invention is to provide a method of producing articlesfrom metal coated sheets wherein the metal coating on the finishedarticle is continuous .and unbroken throughou the entire surface of thearticle.

A further object of the invention is to provide a method of healing orclosing cracks or scratches formed in the metal coating on a sheetduring the die-drawing of the same to shape the article.

A still further object of the invention is to provide an articleproduced by drawing a metal coated sheet, which article has a continuousu'nbroken metal coating throughout the entire surface thereof.

These and other objects will in part be obvious 0 and will in part behereinafter more fully disclosed.

' In the drawing which shows by way of illustration one form of articleexemplifying the inventiona coated metal sheet indicating in'brokenlines the blanks which are to be cut therefrom and shaped into a canend;

Fig. 21s a' plan view of a can 'end'cut from the sheet and shapedpreparatory to applying the same to the can body for double seaming;Fig. 3 is a vertical sectional view diametrically of the can end, on anenlarged scale, and

Fig. 4 is a view showing a portion of a can ,end double seemed to a canbody.

It has been a common practice to coat steel sheets with metal such astin, for the purpose of protecting the steel andpreventing the same fromoxidizing and deteriorating. Ithas also been a common practice to outsuch metal coated is strained to a point where it ruptures andseparates, thus exposing the steel plate to the attack of the oxygen ofthe air. The purpose of the.

present invention is to produce a product and the method of ma ng thesame wherein these spaces or cracks incident to the drawing operationare healed or closed, and whereby this closing of the cracks may beaccomplished without applying any further coating to the shaped article.Tin has a much lower melting point than steel. Applicant has discoveredthat it is pos- Figure l is a perspective viewof a portion of York, ofNew York 1935, Serial-No. 32,937

sible to subject the finished article to the influence of heat and thusrender the metal coating on the sheet steel fluid so that it will flowand close up the cracks in the coating produced during the die-drawingwithout in any way disturb- .ing the sheet steel which gives shape andform to the article.

It is thought that the invention will be better understood by a' moredetail-description of the specific article and the method of making thesame. The article illustrated in the drawing is a can end which isproduced from tin-coated sheet steel. The sheet steel is indicated at Iand the tin coatings thereon are indicated at 2 and 3, both surfacespreferably being coated. The sheet of steel is coated with tin while inthe flat. Blanks are cut from this sheet of steel and are die-shapedinto can ends. The broken lines a, a (Fig. 1) indicate the line ofcutting of the sheet to form the blanks, each blank forming a can 6 end.In Figures 2 and 3 of the drawing, the finished can end is indicated atl. The blank die-shaped to produce the can end. The metal is drawn so asto provide a central panel surrounding which is 'a raised annular rib 5.This is for the purpose of giving strength to the panel and preventingthe same from curving.

one way or the other, due to a differential in pressure on the oppositesides of the end when the receptacle is sealed. The can end is shaped soas to provide a wall 6. This wall is substantially atright angles to theplane of the can end. The purpose of producing this wall is to enablethe endto be joined to the body of the can by a double, seam. In Fig. 4of the drawing, the can end is indicated at I, and itis noted that thiswall 6 extends down into the can end so that a chuck placed in therecess formed in the outer face of the can end will contact with thiswall 6. The flanged portion 1 of the can end is then curled in a wellknown manner into-the double seam 8. This forming of the wall 6 producesa severe strain on the metal coating covering the surface of the steelsheet. This metal surface, particularly in the region indicated at 9 inthe drawing, is so severely strained that it often breaks and separates,forming a crack or a space where the sheet steel is exposed.v There areother portions of the can end wherein the-metal coating is also underseverestrain.

which is likely to fracture the metal coating.

but this particular place referred to will be sum cient to illustratethepurpose of the present invention. This portion'of the end indicatedat 9 is on the inner face of the end when it is attached to the canbody, and as a. consequence, the exposed portion of the steel is likelyto be contacted, not only with the gases in the head space of the can,but the contents of the can 5 itself. Injurious effects upon the foodproduct and also upon the steel forming the end occur from thesefractures of the metal coating incident to die-drawing.

After the end has been shaped by die-drawing,

it is submerged in a heated bath of liquid having a boiling pointsubstantially higher than the melting point of tin. The liquid used forthe bath is preferably one which is water soluble and has a fiuxingre-action. Glycerine is found to be verysuitable for this purpose. Ithas a boiling point of approximately 554? F., which is approximately 112above the melting point of tin. This is still far below the meltingpoint of steel. Therefore, the die-shaped article may be submerged inthe glycerine bath heated to a temperature considerably below itsboiling point. A good workable temperature is 470 F. When the article issubmerged in the heated bath from ten to twenty seconds, the tin coatingwill become fiuid. The glycerine will flux the exposed steel surfacebetween the separated edges of the -tin coating and the metal will flowso as to complete- 1y heal or close up the crack and thus produce acontinuous unbroken tin surface covering the entire surface of thearticle. Glycerine is water soluble and can easily be removed from thesurface of the article when it is taken from the.

bath. In order to activate this fluxing reaction, two to three percenteach of ammonium chloride and zinc chloride is preferably added to theglycerine bath.

Liquids other than glycerine may be used. For

example, diethylene glycol, the boiling point ofwhich is approximately482 E, which is well above the melting point of tin. Any fatty acid,

such as palm oil, oleic acid, stearic acid, and mixtures of these withother oils having'high bolling points could be used. If, however, fattyacids are used then a hydrocarbon solvent would be necessary to cleanthe article after treatment. It

contact of the dies with the metal coating and the excessive strainexerted upon the metal coating din-ing the shaping of the sharp angularportions of the article.

While the invention is described in connection with the making of cansends, it lsyunderstood, .of course, that it may be used in connectionwith other articles which are shaped by die-drawing metal coated sheetsof steel. While sheet is described as coated with tin, it may be themetal coated with other metals having a melting point considerablybelow'that of the steel so that it may be dipped in the bath and themetal coating rendered fluid for the purpose described above. Indescribing the invention and the article, the sheet steel is stated tobe coated with a metal on both faces. It will be understood, of course,that only the face of the metal may be coated which it is desired toprotect. For example, in a can end, it might be desirable to coat withmetal the inner face of the end only, and therefore, the invention isnot limited 'to the coating of both faces of the sheet steel, but isdirected more particularly to the healing or closing of cracks in ametal coating produced by die-drawing. While sheet steel is referred toas the base metal which gives shape and form to the article, it will beunder- I stood that other metals may be used for this purpose, but it isessential to the carrying out F of the method that the base metal shallbe of a higher melting point than the coating metal applied to andcovering the surfaces thereof.

From the above it will be noted that the improved method produces anarticle from a coated metal sheet by die-drawing wherein the finishedarticle has a continuous unbroken metal coating extending throughout theentire surfaces thereof and this is accomplished without any furtherapplication of the coating material to the shaped article. It is obviousthat many changes may be made in the application of the invention and inthe details of the method described and the product produced withoutdeparting from the spirit of the metal coating fluid, causing the sameto flow and thereby closing all cracks and bare spots in themetal-coated surface.

2. The method of producing an article from sheet material consisting incoating a sheet of steel with tin, cutting the sheet to form a blank,die-shaping the blank to form the article, heating the shaped article ina bath of glycerine to which has been added a chloride flux, which bathis raised to a temperature above the melting point of the tin and belowthe melting point of the steel, rendering the metal coating fluid,causing the same to flow and thereby closing all cracks and bare spotsin the metal-coated surface.

ALFRED L. KRONQUEST.

